1. Field of the Invention
The present invention relates to a fuel supply unit for supplying a fuel (in a tank), for example, to an engine and the like of a vehicle.
2. Description of the Related Art
In general, a fuel supply unit of an engine and the like of a vehicle is, on the whole, constituted of a fuel tank for tanking therein a fuel, a cover member mounted to the fuel tank, and a fuel pump disposed substantially below the fuel tank and supplying the fuel {in the fuel tank} to an injection valve and the like on an engine body's side.
The fuel pump is, on the whole, constituted of:                a pump case extending substantially upward and downward;        a motor section disposed on an upside of the pump case and including a stator, a rotor, a brush and the like; and        a pump section which is driven by means of the motor section, sucks a fuel in the fuel tank and discharges the thus sucked fuel outside the fuel tank.        
The pump section is formed with an intake port for taking therein the fuel in the fuel tank, while the pump case has an upper section formed with a discharge port for discharging the fuel.
U.S. Pat. No. 5,782,223 (equivalent of Japanese Patent No. 3256972 or JP3256972B2) discloses a fuel supply unit (referred to as “FUEL SUPPLY SYSTEM”). Driving a pump section by means of a motor section of a fuel pump may intake a fuel from an intake port into the pump section. Then, the pump section may discharge the fuel to the motor section's side. With the above constitution and operation, the fuel is discharged from a discharge port to an injection valve of an engine body's side after passing through a gap (between a stator and a rotor), a periphery of a brush and the like in the motor section.
According to U.S. Pat. No. 5,782,223 (equivalent of Japanese Patent No. 3256972 or JP3256972B2), however, the fuel is delivered from the pump section, through the gap, the periphery of the brush and the like of the motor section, to the engine body's side, thus mixing dust, melt and the like (which may have been caused by wear powder and the like of the brush of the motor section) into the fuel. Thereby, removing the wear powder and the like is expected to be in need for enhanced capacity and performance of a fuel filter, resulting in greater dimension, increased cost and the like of the fuel filter.
Preventing the motor section from corrosion or melt which may be caused by the fuel may be in need for a material with oil-proof. Moreover, preventing the mixture of the wear powder into the fuel may be in need for a material that is unlikely to cause the wear powder to the motor section. This may lead to an increased cost of the material for the motor section, resulting in increased production cost.
The fuel passing through the motor section may become a resistance against rotation of the rotor. In view of a possible loss caused by the resistance, the motor section may be in need for having an increased output, resulting in increased cost in this respect.
Moreover, the fuel passing thought the motor section may cause a heat that may be responsible for an increased temperature of the fuel, causing vapor and the like.